Arteries are made up of three layers, the intima, the media, and the adventitia. The layer that is in direct contact with the flow of blood is the tunica intima, commonly called the intima. The next layer is known as the tunica media, or the muscular layer. The outermost layer is the tunica adventitia or the adventitia, which is composed of connective tissue. The lumen is the channel in an artery through which blood flows. A dissection is a separation in the layers of the artery wall resulting from a tear in the intima—blood flow through the tear enters the arterial wall creating a false lumen, with differing results depending on the location and unique physiology of the tear. The dissection of any of the carotid artery, vertebral artery, coronary artery, or aorta are all serious medical conditions, but even within each of these types, there is wide variability of presentations, complications, and treatments. For example, several different classification systems have been used to describe aortic dissections. The commonly-used Stanford classification is divided into two groups, A and B, depending on whether the ascending aorta is involved. A involves the ascending aorta and/or aortic arch, and possibly the descending aorta, and B involves the descending aorta or the arch (distal to right brachiocephalic artery origin), without involvement of the ascending aorta. Type A ascending aortic dissections generally require primary surgical treatment whereas type B dissections generally are treated medically as initial treatment with surgery reserved for any complications.
Where treatment with medication alone is deemed insufficient for the treatment of a dissection, the goal of surgical intervention is to treat a patient as effectively but as non-invasively as possible in order to minimize post-surgical risks and reduce recovery times. One recognized method of repairing a damaged artery is the endoscopic and endovascular placement of a stent graft or graft to repair the damaged artery. However, stents may not adequately repair the specific damage of the artery in each case, requiring more invasive procedures, or may provide only a temporary solution. A bare stent provides mechanical support for the true lumen but does not seal the intimal tear, allowing for continued perfusion of the false lumen. For example, re-intervention occurred in 81% of Complicated Type B patients in one 82 patient study. (Gotz M. Richter, TEVAR for Acute Type B Dissections Is Not a Single Step Procedure: Permanent Surveillance and Reinterventions May Be Required, VEITH Symposium; New York, N.Y., Nov. 17, 2011). When placed correctly, a grafted stent can cover the intimal tear, but may also occlude collateral arteries. In another example, where a stent graft was used to seal a tear or weak areas of the aortic wall, 25-50% of cases had complications with aortic branch vessels. (Fattori, R. et al., Malperfusion Syndrome in Type B Aortic Dissection: Role of the Endovascular Procedures, Acta Chir Belg 108 (2008): 192-197). In other circumstances a stent or stent graft can seal the primary tear, but a secondary tear will continue to allow blood flow into the false lumen. Therefore, it is desirable to provide a tool that adds additional flexibility and more varied treatment options for blood vessel dissections over known methods and tools.